English Abstract
The Effect of the Imperfections of Network on the Properties of Model Polyurethane Networks
Faculty of Environmental Studies, Nagasaki University, Nagasaki, Japan
Hitachi Zosen Information Systems Co., Ltd., Ota-ku, Tokyo, Japan
Tamaki WomenÕs Junior College, Nagasaki, Japan
Nippon Gomu Kyokaishi,(2006),79(5),271-276 Original Paper in Japanese

The effects of the network imperfections such as dangling chains or abnormally long network chains on the properties of model polyurethane networks were studied. NCO-terminated prepolymer prepared from poly (oxypropylene) glycol with molecular weight 1,000 and 2,4-tolylene diisocyanate were end-linked with trimethylolpropane (TMP). The R-values, the molar ratio of OH group of TMP to NCO group of prepolymer, were varied in wide range. It is expected that dangling chains will form for R<1 and long network chains for R>1. Sol fraction and network chain densities were determined. Sol-free specimens were obtained by careful drying of those attained equilibrium swelling. Glass transition temperature, stress relaxation, dynamic mechanical property, and energy loss in repeated stretching were measured for both the sol-containing and sol-free specimens. The results are as follows. The values of effective network chain density agreed with those calculated from the consideration of network formation for R<1 region, but exceeded for R>1 region. Though the values of properties are related well with the network chain density, the data lie on different plots for R<1 and R>1 region. The results were discussed on the basis of network imperfections.

(Received on December 12, 2005)

(Accepted on February 14, 2006)

Polyurethane, Network, Imperfection, Dangling chain, Energy loss